This invention provides a new fire retardant polytetramethylene ether glycol which is useful as a diol component in making fire retardant esters, and which is useful as a high molecular weight or macro diol ingredient, for example, in preparation of isocyanate prepolymers for polyurethane elastomers, and in the preparation of polyurethane elastomers by the so called one-shot methods in which a high molecular weight diol, a low molecular weight diol, e.g., 1,4-butane diol, and polyisocyanate are reacted directly. The resulting polymers are low temperature-flexible, fire-retardant elastomers having excellent, and in some instances improved properties such as, for example, tear strength and low temperature flexibility as compared to polymers prepared by an otherwise identical procedure and process but made from unmodified polytetramethylene ether glycol.
2,3-DIBROMO-2-BUTENE-1,4-DIOL HAS BEEN USED AS LOW MOLECULAR WEIGHT GLYCOL CHAIN EXTENDER IN PLACE OF ALL OR PART OF A 1,4-BUTANE DIOL INGREDIENT IN POLYURETHANE ART FOR REACTION WITH ISOCYANATE GLYCOL PREPOLYMERS. The resulting polyurethane product was generally crystalline, and had low resiliency. Even though the use of 2,3-dibromo-2-butene-1,4diol as the low molecular weight glycol chain extender has been known for three or four years, the undesirable hard, crystalline physical characteristics of the resulting elastomer has resulted, to the best of our present understanding, in very slow, if any, commercial adoption of this avenue towards providing improved fire retardant elastomers.
The use of polytetramethylene ether glycol, also known as poly(tetramethylene glycol) in the patent art, is widely known and well established as a high molecular weight diol in the manufacture of polyurethane and polyester elastomers.
It is an object of the present invention to provide a novel, modified polytetramethylene ether glycol which has improved fire resistance, which has physical and chemical properties substantially identical to those of the commercially established polytetramethylene ether glycols and which is useful as a reactive fire retardant in the manufacture of polyester and polyurethane compositions. Generally speaking, so called reactive flame retardants are preferred, in many respects, to the so called non-reactive flame retardants which are merely incorporated into elastomers mechanically or physically, and which are not chemically integrated in the elastomer molecule. The modified polytetramethylene ether glycol, in accordance with the present invention, provides a non-fugitive fire retardant component which will not migrate, be lost by solvent extraction, nor be volatilized, thus providing an extremely high level of permanence with respect to the fire retardant characteristics. In addition, in accordance with the present invention, the fire retardant component or ingredient provides a process convenience inasmuch as the use of polytetramethylene ether glycol is now well established with respect to polyester and polyurethane art, and inasmuch as the fire retardant modified polytetramethylene ether glycol in accordance with the present invention is incorporated into the elastomers and other polymers using known, established procedures. Additionally the bother associated with an additional ingredient is obviated as well as the problem of obtaining uniform distribution of an "inert" additive in the polymer matrix.
It is becoming increasingly more widely appreciated that fire retardant characteristics are provided by incorporating halogen-containing components into elastomers and other polymers. However, the halogenation of polytetramethylene ether glycol polymers by direct halogenation results primarily in alpha-halo ethers, and the chemical instability of alpha-halo ethers is well known. Chemically unstable halogen-containing polytetramethylene ether glycols would be regarded as unsuitable for use in the manufacture of polyurethanes, because the hydro-halic acid evolved would cause what would be regarded as intolerable levels and variation in the acid number. The compounds in accordance with the present invention are surprisingly stable with respect to chemical and physical properties.
In its broadest aspects, the present invention provides novel modified polytetramethylene ether glycols of the following formula: ##STR1## wherein m and n is an integer, can include zero, and wherein both m and n cannot be zero at the same time, and wherein X is: ##STR2## and wherein m and n are integers such that the number average molecular weight of the composition is in the range 400-5000 molecular weight inclusive.
The presently contemplated best mode for producing the modified polytetramethylene ether glycol in accordance with the present invention comprises reacting 2,3-dibromo-2-butene-1,4-diol with the catalytically active tetrahydrofuran-catalyst-polymer mixture which is formed as a result of the reaction of tetrahydrofuran and a tetrahydrofuran polymerization catalyst. The unsaturated monomeric bromo diol is added to the catalytically active mixture, and is permitted to react with the catalytically active tetrahydrofuran polymer prior to the termination of the remaining catalytic activity of the mixture by reaction with excess of water. The polymerization of tetrahydrofuran is discussed at great length in U.S. Pat. No. 3,454,652 to Andrew P. Dunlop and Edward Sherman for "Process for Producing Tetrahydrofuran Polymers". In that patent, the patentees describe in considerable detail the polymerization of tetrahydrofuran(THF), and, in addition, disclose a list of catalysts for polymerization of tetrahydrofuran, as well as a number of catalytic activity terminating agents. Catalytically active THF-catalyst-polymer mixture for use in accordance with the present invention can be made using any of the procedures set forth in that patent. Also, in accordance with the present invention, any of the catalytic activity termination agents set forth in that patent can be used, although the use of water or 1,4-butane diol is preferred.
It is not necessary that the temperature of the reaction mixtures be lowered prior to termination of catalytic activity. As set forth in the following discussion, it is preferred to permit the 2,3-dibromo-2-butene-1,4-diol to react at slightly elevated temperatures e.g. at 60.degree. C. and above, prior to the catalytic activity termination.